Publications

We show that global political uncertainty, measured by the U.S. election cycle, on average, leads to a fall in equity returns in 50 non-U.S. countries. At the same time, market volatilities rise, local currencies depreciate, and sovereign bond returns increase. The effect of global political uncertainty on equity prices increases with the level of uncertainty in U.S. election outcomes, and a country’s equity market exposure to foreign investors, but does not vary with the country’s international trade exposure. These findings suggest that global political uncertainty causes an increase in investors’ aggregate risk aversion, leading to a flight to safer assets.

We study the impact of index investing on firm performance by examining the link between commodity indices and firms that use index commodities. Starting in 2004, there was a dramatic increase in commodity index investing, an event referred to as the financialization of commodity markets. Following financialization, firms that use index commodities make worse production decisions and earn lower profits. Consistent with a feedback channel in which market participants learn from prices, our results suggest that index investing in financial markets distorts the price signal thereby generating a negative externality that impedes firms' ability to make production decisions.

Adverse selection in financial markets is traditionally measured by the correlation between the direction of market order trading and price movements. We show this relationship has weakened dramatically with limit orders playing a larger role in price discovery and with high-frequency traders’ (HFTs) limit orders playing the largest role. HFTs are responsible for 60–80% of price discovery, primarily through their limit orders. HFTs’ limit orders have 50% larger price impact than non-HFTs’ limit orders, and HFTs submit limit orders 50% more frequently. HFTs react more to activity by non-HFTs than the reverse. HFTs react more to messages both within and across stock exchanges.

Theory on high-frequency traders (HFT) predicts that market liquidity for a security decreases in the number of HFT trading the security. We test this prediction by studying a new Canadian stock exchange, Alpha, that experienced the entry of 11 HFT firms over four years. Bid-ask spreads on Alpha converge to those at the Toronto Stock Exchange as more HFT trade on Alpha. Effective and realized spreads for nonHFT improve as HFT firms enter the market. To explain the contrast with theoretical predictions we test the model assumption of price competition and reject it in favor of quantity competition.

We study performance and competition among high-frequency traders (HFTs). We construct measures of latency and find that differences in relative latency account for large differences in HFTs’ trading performance. HFTs that improve their latency rank due to colocation upgrades see improved trading performance. The stronger performance associated with speed comes through both the short-lived information channel and the risk management channel, and speed is useful for a variety of strategies including market making and cross-market arbitrage. We explore implications of competition on relative latency and find support for various theoretical predictions.

Prior research documents no significant abnormal returns around upgrades of credit ratings, suggesting that upgrades do not convey new information. These tests are limited by lack of data, liquidity screens, and ambiguous predictions. We extend prior research using trading volume. Because volume is highly non-normally distributed (especially in the bond market), we derive a new, more powerful nonparametric test statistic that can be used in other applications. Our results show significant abnormal volume in both stock and bond markets around both upgrades and downgrades. Some of this volume is attributable to credit-ratings-based regulations and other factors. Controlling for other effects, we also find evidence that upgrade announcements contain information.

Do banks’ responses to changes in deposit insurance vary across countries even if the countries have comparable institutions? If so, by how much? Using data on the financial performance of large banks in 15 financially and economically developed countries, we find that where deposit insurance has an effect, it is large and varies depending on the level of economic freedom, rule of law and corruption in the bank’s home country. As in prior papers, we show that during stable economic periods, increases in deposit insurance are associated with higher bank risk, both problem loans and leverage. In most, but not all cases, stronger institutions temper these effects. The institutions’ effects are substantial. For example, average changes in the Rule of Law double the impact of a change in deposit insurance on bank leverage. We contribute to the substantial literature in this area by showing that the institutional effects are significant even across a set of countries with comparable institutions; by conducting a careful calibration of the economic significance of the effects; by providing evidence that during stable periods changes in deposit insurance only affect bank risk and not other measures of performance; and finally by showing that the effects of both deposit insurance and institutions vary across stable and crisis economic periods. The stable period results are consistent with the moral hazard effects of deposit insurance, while the crisis period results are consistent with endogeneity concerns that poor bank performance could drive changes in regulations.

Using a sample of all academics who pass through top 50 economics and finance departments from 1996 through 2014, we study whether the granting of tenure leads faculty to pursue riskier ideas. We use the extreme tails of ex-post citations as our measure of risk and find that both the number of publications and the portion consisting of “home runs” peak at tenure and fall steadily for a decade thereafter. Similar patterns hold for faculty at elite (top 10) institutions and for faculty who take differing time to tenure. We find the opposite pattern among poorly-cited publications: their numbers rise post-tenure.

Are endogenous liquidity providers (ELPs) reliable in times of market stress? We examine the activity of a common ELP type – high frequency traders (HFTs) – around extreme price movements (EPMs). We find that on average HFTs provide liquidity during EPMs by absorbing imbalances created by non-high frequency traders (nHFTs). Yet HFT liquidity provision is limited to EPMs in single stocks. When several stocks experience simultaneous EPMs, HFT liquidity demand dominates their supply. There is little evidence of HFTs causing EPMs.

This paper examines the impact of stock liquidity on firm bankruptcy risk. Using the Securities and Exchange Commission’s decimalization regulation as a shock to stock liquidity, we establish that enhanced liquidity decreases default risk. Stocks with the highest default risk experience the largest improvements. We find two mechanisms through which stock liquidity reduces firm default risk: through improving stock price informational efficiency and facilitating corporate governance by blockholders. Of the two mechanisms, the informational efficiency channel has higher explanatory power than the corporate governance channel.

We examine the effects of high-frequency traders (HFTs) on liquidity using the September 2008 short sale-ban. To disentangle the separate impacts of short selling by HFTs and non-HFTs, we use an instrumental variables approach exploiting differences in the ban’s cross-sectional impact on HFTs and non-HFTs. Non-HFTs’ short selling improves liquidity, as measured by bid-ask spreads. HFTs’ short selling has the opposite effect by adversely selecting limit orders, which can decrease liquidity supplier competition and reduce trading by non-HFTs. The results highlight that some HFTs’ activities are harmful to liquidity during the extremely volatile short-sale ban period.

We exploit an optional colocation upgrade at NASDAQ OMX Stockholm to assess how speed affects market liquidity. Liquidity improves for the overall market and even for noncolocated trading entities. We find that the upgrade is pursued mainly by participants who engage in market making. Those that upgrade use their enhanced speed to reduce their exposure to adverse selection and to relax their inventory constraints. In particular, the upgraded trading entities remain competitive at the best bid and offer even when their inventories are in their top decile. Our results suggest that increasing the speed of market-making participants benefits market liquidity.

Using the news-based measure of Baker et al. [Baker SR, Bloom N, Davis SJ (2013) Measuring economic policy uncertainty. Working paper, Stanford University, Stanford, CA] to capture economic policy uncertainty (EPU) in the United States, we find that EPU positively forecasts log excess market returns. An increase of one standard deviation in EPU is associated with a 1.5% increase in forecasted three-month abnormal returns (6.1% annualized). Furthermore, innovations in EPU earn a significant negative risk premium in the Fama–French 25 size–momentum portfolios. Among the Fama–French 25 portfolios formed on size and momentum returns, the portfolio with the greatest EPU beta underperforms the portfolio with the lowest EPU beta by 5.53% per annum, controlling for exposure to the Carhart four factors as well as implied and realized volatility. These findings suggest that EPU is an economically important risk factor for equities.

This paper studies whether high-frequency trading (HFT) increases the execution costs of institutional investors. We use technology upgrades that lower the latency of the London Stock Exchange to obtain variation in the level of HFT over time. Following upgrades, the level of HFT increases. Around these shocks to HFT institutional traders’ costs remain unchanged. We find no clear evidence that HFT impacts institutional execution costs.

We examine the role of high-frequency traders (HFTs) in price discovery and price efficiency. Overall HFTs facilitate price efficiency by trading in the direction of permanent price changes and in the opposite direction of transitory pricing errors, both on average and on the highest volatility days. This is done through their liquidity demanding orders. In contrast, HFTs' liquidity supplying orders are adversely selected. The direction of HFTs' trading predicts price changes over short horizons measured in seconds. The direction of HFTs' trading is correlated with public information, such as macro news announcements, market-wide price movements, and limit order book imbalances.

Using detailed publication and citation data for over 50,000 articles from 30 major economics and finance journals, we investigate whether network proximity to an editor influences research productivity. During an editor's tenure, his current university colleagues publish about 100% more papers in the editor's journal, compared to years when he is not editor. In contrast to editorial nepotism, such “inside” articles have significantly higher ex post citation counts, even when same-journal and self-cites are excluded. Our results thus suggest that despite potential conflicts of interest faced by editors, personal associations are used to improve selection decisions.

Under Review

We examine whether an external governance mechanism, Bilateral Investment Treaties (BITs), remove impediments to cross-border mergers by protecting the property rights of foreign acquirers. We find that BITs have a large, positive effect on cross-border mergers. The probability and dollar volume of mergers between two given countries more than doubles after the signing of a BIT. Most of this increase is driven by deals flowing from developed economies to developing economies. The effect of BITs is concentrated in target countries with medium levels of political risk, consistent with views that BITs are ineffective for countries with very high country risk and unnecessary for countries with low country risk. Overall the results suggest that some countries outsource legal protection when institutions are not fully developed.

Whether banks and stock markets are substitutes or complements is much debated. We use an exogenous shock to capital market development, liquidity, to test whether stock markets complement or compete with banks. We find that greater stock price liquidity increases banks’ willingness to participate in syndication leading to more dispersed syndicated loan structures. The channel is through enhanced stock price informativeness that allows potential participant banks to learn more about the borrowing firm, reducing the adverse selection costs associated with syndication. Furthermore, we show that this feedback effect from markets to banks more generally improves corporate access to bank credit.

Theory suggests dark pools may facilitate or discourage price informativeness. We find that more dark trading leads to greater firm-specific fundamentals in stock prices. To overcome endogeneity concerns we exploit the SEC’s Tick-Size Pilot Program that resulted in a large exogenous shock to dark pool trading. The results remain. The results cannot be explained by lit market liquidity, high frequency trading, or price efficiency. In support of the information acquisition interpretation, we find a shift in the information acquisition through SEC EDGAR searches for the treatment firms. Overall, the evidence suggests dark trading improves the price informativeness of stock prices.

Recent advances in machine learning methodologies have improved the usefulness of the technology. This paper examines whether machine learning using only past prices as the input can detect mispricings. Generally searching for mispricings is a slow process and can easily suffer from data-snooping. This paper provides a machine learning algorithm to search for mispricings while controlling for data-snooping. The process generates significant out-of-sample alpha. Overall, the results show that mispricings still exist, but have decreased over time, implying that markets have recently become more efficient.

This paper provides novel evidence that corporate political influence operates through renegotiations of existing government contracts. Using detailed data on contractual terms and renegotiations around sudden deaths and resignations of local politicians, the estimates show that politically connected firms initially bid low and successfully renegotiate contract amounts, deadlines, and incentives. The effects hold across different industries and contract types, enhance firm value, and persist around the exogenous increase in contract supply due to the American Recovery and Reinvestment Act of 2009. Overall, this paper puts forth an unexplored link between political influence, ex-post renegotiations and ex-ante bidding of government contracts.

We develop a return variance decomposition model to separate the role of different types of information and noise in stock price movements. We disentangle four components: market-wide information, private firm-specific information revealed through trading, firm-specific information revealed through public sources, and noise. 31% of the return variance is from noise, 37% from public firm-specific information, 24% from private firm-specific information and 8% from market-wide information. Since the mid 1990s there has been a dramatic decline in noise. During this period firm-specific information is increasing, consistent with increasing market efficiency. Our findings help reconcile the mixed results in the R^2 literature.

Working Papers

To maximize firm value managers must efficiently invest new capital. This paper examines whether analyst coverage impacts a firm’s investment efficiency. Using broker mergers and closures as exogenous shocks to the number of analysts covering a firm, we find that firm investment efficiency significantly decreases after losing an analyst. The impact is largest for firms with the fewest number of analysts. We find evidence that the effect is driven by the role analysts play in information acquisition and in price efficiency. Our results suggest that the recent decline in analyst coverage may negatively impact resource allocation and future firm performance.

We investigate whether financial innovation, specifically the introduction of derivative products, spurs firms’ real innovation, measured with patent based metrics. Consistent with financial innovation being an important contribution to real innovation, we find that the use of financial derivatives causes firm patent production to increase. The main mechanism behind the relationship is improved risk management. Derivatives usage decreases cash flow volatility, decreasing the need for external financing, and allowing firms to expand their innovative projects.

Trade information leakage is a prominent feature in modern equity markets. We study the usage of multiple brokers to help mitigate information leakage. We first document that multi-broker trades are larger and more profitable than single-broker trades, consistent with multi-broker trades being likely to be driven by information motives. When conditioning on the trade size, we find that multi-broker trades have smaller price impacts, dramatically larger long-term trade profitability, and a significantly smaller number of followers’ trades in the same direction than matched single-broker trades. It appears that informed traders split their best trading ideas across multiple brokers to avoid the likelihood and impact of broker level information leakage.

This paper studies the effects of price limits implemented by the Securities and Exchange Commission (SEC) after the May 2010 ‘Flash Crash.’ The security-level price limits halt trading after a security’s price experiences a sudden and large movement. The difference-in-difference design exploits the staggered introduction of the limits to address omitted variable concerns. The data show that price limits reduce the frequency and severity of extreme price movements, but induce price underreaction. The results are consistent with Subrahmanyam’s (1997) theory that price limits cause informed traders to be less aggressive.

The May 2010 Flash Crash and August 2007 Quant Meltdown raised concerns about the impact of quantitative investment strategies on market stability. Theory is split on whether quantitative investing dampens or exacerbates market instability. To test the theory we focus on mutual fund fire sales. We find that quantitative fund fire sales have a much larger impact on market instability than fire sales by traditional mutual funds. For the same magnitude fire sale, quantitative funds’ impact is over five times as large. The evidence suggests this is due to quantitative funds’ reliance on similar trading signals and sensitivity to the time-series of returns.